The invention relates to a process and an apparatus for producing liquid pig iron or liquid primary steel products from charge materials formed by iron ores and additions. The charge materials are subjected to a further reduction in a reducing zone. The materials are then fed to a smelting zone or a smelting unit, in particular a fusion gasifier, for smelting with the addition of carbon carriers and oxygen-containing gas to form a fixed bed. A CO- and H2-containing reduction gas is formed, that gas is introduced into the reducing zone, is converted there and is drawn off as top gas. The hot top gas, laden with solid matter, is subjected at least to a dry dust separation, in particular a coarse separation, with at least partial separation of the solids from the top gas. At least parts of the separated hot solids are returned into the smelting zone or the smelting unit or into a reducing zone.
It is known from the prior art on the one hand that process gases are used in various process stages or in combined processes but on the other hand that drawn-off process gases have to be treated to allow them to be passed on for further use. For this purpose, known processes often use cleaning processes for the drawn-off process gases, wherein the gases have to be cooled, with the result that considerable energy has to be removed and heat content is lost.
JP 05-078722A describes a smelting reduction process in which the top gas has the dust removed when hot, and the dust is introduced together with pre-reduced material into the smelting unit. A particularly disadvantageous aspect of this is that hot-gas cyclones only achieve inadequate dedusting.
It is known from AT 406964 B to use the waste heat of top gas from a reducing unit, preceded by hot-gas filtering. No solution is given to the problem of reusing the dusts.
It is similarly known from WO 2005/054520 to clean top gas by means of a scrubber and to pass the top gas on for renewed use. A disadvantageous aspect of this is the large amount of slurries produced.